JP4343435B2 - Printing machine and printing plate cleaning method - Google Patents

Abstract

A process is proposed for cleaning printing machines or printing plates by removing the contaminants from the surfaces to be cleaned by washing them with a microemulsion comprising water, a surfactant, and a water-immiscible organic solvent.

Description

[0001]
The invention relates to cleaning printing presses and printing plates, in particular printing inks such as oil-based printing inks or radiation-curing printing inks from cylinders or rollers of printing presses, in particular flat or offset printing presses, and The invention relates to a method for removal from a printing plate, for example when the printing process is interrupted.
[0002]
For these purposes, cleaning agents based on organic solvents and / or aqueous solutions are generally used. At that time, when the machine is stopped for a long time at the printing station or when the ink is changed, the remaining ink is removed from the portion of the printing press that has come into contact with the printing ink. Similarly, when the printing process is interrupted, it is carefully coated with a storage solution based on a hydrophilic polymer to carefully clean the remainder of the ink from the printing plate, especially the flat printing plate, and to preserve the hydrophilicity of the non-image areas. I have to do it. Cleaners containing organic solvents often contain volatile organic compounds (VOC), which are environmentally friendly and have occupational and ecological concerns. . A cleaner consisting only of a nonpolar organic solvent or mostly nonpolar organic solvent has the further disadvantage that the part to be cleaned, for example the remainder of the solvent adhering to the printing roller, cannot be washed away with water after cleaning. However, a clean printing roll is a prerequisite for good wetting with printing ink and good ink transfer. For many printing plates, the printing plate that guides the ink is partially dissolved by the cleaning agent and can be damaged or even unusable.
[0003]
DE-B 2 724 557 describes a cleaning agent for lithographic printing plates, which contains water and an organic solvent immiscible with water. The cleaning action on oily viscous printing inks is of course limited.
[0004]
GB-A 2089289 describes oil-in-water emulsions and water-in-oil emulsions as cleaners. In this case, the relatively high interfacial tension between the aqueous phase and the oil phase is a disadvantage, so that, for example, oleophilic and highly hydrophobic offset inks are based on their high interfacial energy compared to aqueous aqueous cleaner solutions. Only slowly and only to a small extent by the cleaner.
[0005]
The same applies for the emulsions described, for example, in WO-A 90/03419 or EP-A 0498545.
[0006]
In addition, this type of emulsion is only kinetically stable and not thermodynamically stable, so it tends to separate (creaming), thicken, and agglomerate, especially during temperature changes. And this impairs its applicability.
[0007]
Particularly difficult is the removal of UV curable offset inks or letterpress inks based on polymerizable monomers or oligomeric acrylates. An ester or a mixture of ester and mineral oil is generally used for the removal.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning method that quickly and effectively removes printing ink and does not burden the environment with vapors of volatile organic components or corrodes the printing plate of the printing plate. It was to provide a liquid cleaning agent.
[0009]
The present invention starts from a cleaning method for a printing press or printing plate, in which dirt is removed from the surface by washing with a liquid.
[0010]
The process according to the invention is characterized in that the liquid is advantageously a bikontinuierlich microemulsion containing water, a surfactant and an organic solvent immiscible with water as oil phase.
[0011]
Microemulsions are liquid within the scope of the description of the present invention, and advantageously have a very low interfacial tension between the water phase and the oil phase, i.e. 10 less than the usual water-in-oil or oil-in-water emulsions. It is to be interpreted as a composite continuous mixture consisting of an aqueous phase and an oil phase with a low interfacial tension up to the third power. For microemulsions, the interfacial tension is 10 ^- 3-10 ^- in the range of 6 N / m, the case of the emulsion, usually 10 ^{- - 7,} preferably ^{10 - 4 ~10 3 ~10 - 2} N / m It is. Within the scope of the description of the invention, the microemulsion is thermodynamically stable, visually transparent and advantageously low viscosity.
[0012]
Conventional conventional emulsions may contain oil and water phases in very different volume ratios. These phases have a continuous phase and a dispersed phase present in the continuous phase as very small globules that are stabilized by coating with a surfactant. Depending on the nature of the continuous phase, it is called an oil-in-water emulsion or a water-in-oil emulsion. These emulsions are ideally kinetically stable, i.e. they are held for a relatively long time, but not indefinitely. Especially when the temperature changes, the emulsion tends to phase separate due to sedimentation, creaming, thickening or aggregation. A composite continuous microemulsion has two phases, an aqueous phase and an oil phase, in the form of an enlarged, juxtaposed, and intertwined region that stabilizes at the boundary of the region The agent accumulates as a monolayer. Complex continuous microemulsions are formed very easily, usually with a very low interfacial tension, when mixed with the individual components water, oil and a suitable surfactant system. Since the area in at least one dimension has a negligible extension on the order of nanometers, the microemulsion is visually transparent and thermodynamic in a specific temperature range depending on the surfactant system used In other words, it is stable indefinitely in time.
[0013]
Composite continuous microemulsions are described, for example, in the article “Mikroemulsionen-eine wissenschaftliche und anwendungstechnische Fundgrube?” By HF Eicke in SEOFW-Journal 118 (1992), pages 311 to 314.
[0014]
In order to achieve the low interfacial tension required at the phase boundary, the microemulsion contains a specific amphiphile, a surfactant, and its aqueous phase is often separated by dissolved electrolytes and optionally. Contains auxiliary agents. The electrolyte is added especially when the amphiphile is partially or exclusively an ionic surfactant.
[0015]
The use of microemulsions to extract organic harmful substances from contaminated soil is described in WO 94/04289. Tertiary recovery of oil (Tertiaerfoerderung) is also known as an application area of microemulsions.
[0016]
Furthermore, from EP-A-0498545, microemulsions are known as cleaning agents for pretreatment, for example for painted or untreated metal sheets, plastics and other surfaces, in particular for subsequent coatings. .
[0017]
According to another embodiment of the invention, a cleaning agent for the implementation of the method according to the invention is proposed, which consists of a microemulsion comprising water, a surfactant and an organic solvent immiscible with water.
[0018]
The components of the microemulsion are obtained by swelling or shrinking (de-swelling) the mechanical properties, such as elasticity, flexibility, dimensional stability, etc. of the sealing material comprising the device member or rubber or similar material. You should choose not to change.
[0019]
As organic solvents which are not miscible with water, use is advantageously made of solvents having a boiling point of above 100 ° C., preferably above 150 ° C., in particular from 200 ° C. to 400 ° C. In general, an organic solvent having a flash point exceeding 100 ° C. is used. “Organic solvents” are understood in particular as fats and oils, such as rapeseed oil, fatty acid esters, ethers, ketones, aldehydes and hydrocarbons.
[0020]
In general, esters of long chain fatty acids, especially alkyl esters, are suitable. The alkyl group of the alcohol component generally has 1 to 20, preferably 1 to 16 carbon atoms. The fatty acid component usually has 6 to 25, preferably 8 to 18 carbon atoms and may be linear or branched, saturated or unsaturated, and 3 in the molecule. It may have up to two double bonds. The esters generally have an iodine number in the range of 0 to about 150, preferably 0 to 40. Compounds with a high double bond content often become resinous and thus tend to separate unwanted substances. Therefore, if such a compound is added, it is added only in a small proportion. Examples of suitable esters are fatty acids or fatty acid mixtures such as octanoic acid, 2-ethylhexanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, behenic acid or soybean oil-, palm kernel oil -Palm oil-, sunflower oil-, whale oil-, tall oil-, rapeseed oil-, castor oil-or tallow fatty acid methyl ester, ethyl ester, isopropyl ester, n-butyl ester, n-hexyl ester, 2-ethylhexyl ester and / Or isooctyl ester. Individual representative esters include, for example, palm oil acid-2-ethylhexyl ester, tall oil fatty acid-n-hexyl ester, rapeseed oil methyl ester, oleic acid-methyl ester, stearic acid-methyl ester, palmitic acid-isopropyl ester, Lauric acid-ethyl ester, 2-ethylhexanoic acid-2-ethylhexyl ester and octanoic acid-n-octyl ester. Besides these esters, ethers having a high boiling range, such as dioctyl ether, and triglycerides such as rapeseed oil, coconut oil or soybean oil are also suitable.
[0021]
Esters are superior due to their extremely low vapor pressures, so there is no environmental impact during their use. As is customary in complex continuous microemulsions, the volume ratio of aqueous phase to organic phase is approximately of the same order, ie the volume ratio of water to organic phase is generally from 10:90 to 90:10, advantageously 25:75 to 75:25, especially 40:60 to 60:40.
[0022]
As surfactants, hereinafter also referred to as surfactants, various amphiphilic properties are used, namely anionic, cationic, amphoteric and nonionic surfactants or mixtures thereof.
[0023]
Suitable anionic surface active _agents, C 10 _{-C 20} -, preferably _C 12 _{-C 16} - alkyl sulfates such as sodium dodecyl _{sulfate; C} 10 ~C ₂₀ -, preferably _C 12 _{-C 16} Alkyl polyether sulfates, such as sodium dodecyloxypolyethoxy sulfate; alkali salts of diisooctyl sulfosuccinic acid; alkali salts of alkyl benzene sulfonic acids, such as sodium dodecyl benzene sulfonate, alkali salts of dialkyl phosphates, and carboxylates, such as Alkali salt of fatty alkyl ether carboxylate. Some anionic surfactants such as sodium dodecyl sulfate are often used together with alkanols such as butanol, pentanol or hexanol and / or alkali or alkaline earth salts as auxiliary surfactants (Co-Tenside) For example with sodium chloride, sodium sulfate or calcium chloride or with other electrolytes such as NaOH, KOH, phosphates or silicates.
[0024]
Furthermore, the microemulsions used according to the invention may further contain complexing agents such as ethylenediaminetetraacetic acid, nitrilotriacetic acid or methylglycine diacetic acid, corrosion inhibitors and / or preservatives.
[0025]
The alkanol can be added in an amount up to 20% by weight, preferably up to 10% by weight and the electrolyte in an amount up to 10% by weight, preferably up to 5% by weight.
[0026]
For example, alkyltrimethylammonium halides and / or quaternized imidazolinium or pyridinium salts having an alkyl chain length of about 8 to 18 carbon atoms are used for the production of microemulsions as cationic surfactants. be able to.
[0027]
Suitable nonionic or nonionogenic surfactants are C ₈ -C ₁₈ , preferably C ₁₀ -C ₁₆ alkyl chain lengths and 2-20, preferably 3-15 oxyalkylene units, in particular -Polyglycol monoalkyl ethers having ethylene, -propylene and / or -butylene units, or block copolymers composed of these units. Often C _10- to C ₁₅ -alkyl ethers of polyglycols having 3 to 10 oxyalkylene units are used. This is usually an industrial product with varying molecular weight distributions to varying degrees. Surfactants with a narrow molecular weight distribution produced with special catalysts can also be used. Furthermore, triglyceride alkoxylates, for example reaction products of 1 mol of triglycerides with 1 to 50 mol of alkylene oxide, in particular 10 to 50 mol of ethylene oxide, are suitable. In addition, surfactants based on saccharides such as alkylpolyglucosides or glucosamides can be used.
[0028]
The microemulsions used according to the invention advantageously contain anionic surfactants, often in combination with one or more nonionic surfactants. However, microemulsions can also be produced simply by using nonionic surfactants.
[0029]
In order to achieve an optimal cleaning effect, in the individual case for each combination of organic solvent, surfactant or surfactant and optionally electrolyte and complexing agent in aqueous solution, a specific, relatively A narrow quantitative ratio range is required, which can be confirmed by easy routine testing. In general, the proportion of surfactant in the microemulsion is in the range from 1 to 35% by weight, preferably from 1 to 25% by weight and in particular from 7 to 25% by weight. If the ratio of the surfactant is too large, a cleaning problem may occur or it may be difficult to dry the printing roller.
[0030]
1 to 20% by weight of anionic surfactant, preferably 3 to 15% by weight and in particular 5 to 10% by weight; polyethylene glycol monoalkyl ether 1 to 20% by weight; reaction product of triglyceride and ethylene oxide 0.1 1 to 20% by weight, preferably 0.5 to 5% by weight and preferably 1 to 20% by weight of polyalkylene glycol monoalkyl ethers having oxyethylene units and / or oxypropylene units.
[0031]
The microemulsions used according to the invention generally contain from 5 to 60% by weight of an organic solvent immiscible with water, preferably from 20 to 60% by weight, and from 20 to 80% by weight, preferably from 30 to 60% by weight. ing. All descriptions in mass% are here based on the total mass of the finished microemulsion.
[0032]
Each microemulsion is thermodynamically stable over a specific temperature range. Preference is given to microemulsions which are thermodynamically stable below room temperature. In many cases, however, microemulsions whose stability range exceeds room temperature, for example 50-60 ° C., can also be used advantageously.
[0033]
High concentrations of surfactants in known cleaning fluids are often associated with the deposition of surfactants on the printing roll, leading to adverse printing ink stripping. These disadvantages do not occur with the microemulsions used according to the invention.
[0034]
In carrying out the cleaning method according to the invention, the microemulsion is applied to the part of the printing press to be cleaned. The surface of the printing ink is wetted quickly, uniformly and completely, and the printing ink is rapidly taken up by the cleaning liquid and dissolves or emulsifies. The remaining microemulsion residue can be easily removed by washing with water. The same applies to the remainder of the ink remaining on the printing plate to be cleaned and stored after interrupting printing, in particular on the offset printing plate or letterpress printing plate. What is important here is in particular the non-image area or background of the printing plate on which the hydrophilicity required for resuming the printing process, for example during flat printing or offset printing, must be retained. To completely remove the rest of the ink from the part. Within the scope of the description of the present invention, it means a printing plate that is usually ready for printing, obtained by irradiation and development of a photosensitive printing plate.
[0035]
The microemulsions used according to the invention are also suitable for the cleaning of other substances such as plastics, old paints, priming and untreated metal plates. The microemulsions can be used, for example, as cleaning agents in the field of automotive repair painting and as brushing cleaners.
[0036]
The following examples describe in detail the embodiment of the process according to the invention and the microemulsion used in the process and the preparation thereof.
[0037]
Production Example 1
10 g dioctylsulfosuccinate (sodium salt), 7 g polyglycol monoalkyl ether mixture having about 5 oxyethylene units and one C ₁₀ -C ₁₃ -alkyl ether group, 46 g C ₈ -C ₁₈ -fatty acid methyl ester mixture, By mixing 37 g of water and 0.07 g of calcium chloride and shaking the mixture for a short time, a low-viscosity microemulsion that was thermodynamically stable at room temperature and transparent to the eye was obtained.
[0038]
Production Example 2
A room temperature stable microemulsion was prepared as described in Preparation Example 1, except that 8 g of dioctyl sulfosuccinate, 16 g of the same polyglycol monoalkyl ether mixture, 15 g of rapeseed oil fatty acid methyl ester, coconut oil Prepared from 15 g of fatty acid-2-ethyl-hexyl ester, 46 g of water and 0.07 g of calcium chloride.
[0039]
Production Example 3
A microemulsion was obtained by mixing in the same manner as in Production Example 1 from 14 g of dioctyl sulfosuccinate, 34.5 g of soybean oil and 51.5 g of water. The microemulsion is thermodynamically stable in the temperature range of 55-58 ° C. and is visually transparent.
[0040]
Production Example 4
17.0 g of dioctyl sulfosuccinate was dissolved in 41.5 g of water and the solution was mixed with 415 g of decane. The mixture formed a visually low-viscosity microemulsion that was thermodynamically stable in the temperature range of 51-56 ° C.
[0041]
The microemulsions of Production Examples 3 and 4 were not continuously stable outside the stated temperature range, and separated into an oil phase and an aqueous phase after relatively long standing at room temperature. In contrast, the microemulsions of Production Examples 1 and 2 can be used for an unlimited period at room temperature.
[0042]
Application example 5
In a comparative test, the rollers of a rotary offset printing press were each printed with a white spirit (mainly an aliphatic hydrocarbon having a boiling point range of 80 to 250 ° C.) after 100,000 times printing using a commercially available oil-based offset ink, and a production example Cleaned once with microemulsion according to 1. In all cases, the cleaning results, i.e. the removal of the printing ink, were substantially the same. With the microemulsion, the cleaned roller was much cleaner and dry than with white spirit. The remainder of the microemulsion could also be removed easily and without residue by simple washing with water.
[0043]
Similarly, the offset printing plate used in the printing process was treated with both cleaner solutions. In all cases, a printing plate was obtained which was clean and free from ink residue. The printing plate cleaned with the microemulsion was smooth and completely wetted with the aqueous solution of gum arabic applied thereafter, while it was cleaned with the white spirit, depending on the support surface of the printing plate forming the non-image area. However, the solution was difficult to accept and was only accepted by relatively long intensive treatments.

Claims (2)

In a method of cleaning a printing press or printing plate that removes contaminants from a surface to be cleaned by washing with a liquid, the liquid comprises:
a) _C 8 saturated or unsaturated as an organic solvent immiscible with water _{-C 25} - fatty acids of _C 1 _{-C 20} - alkyl esters of 20 to 60 wt%,
b) 30 to 60% by mass of water containing a water-soluble alkali metal salt or alkaline earth metal salt ,
c) at least one of A anion surfactant and at least one non-ionic surfactant 7-25 wt%
In which the water to organic phase volume ratio is 40:60 to 60:40 , wherein the anionic surfactant is dioctyl sulfosuccinate , and non-ionic surfactants is characterized by that you have selected from the group consisting of polyglycol monoalkyl ethers with alkyl chain lengths and 2-20 oxyalkylene units C ₈ -C _18, How to clean a printing press or printing plate. The method according to claim 1 , wherein the complexing agent or the corrosion inhibitor is dissolved in water.